Paving asphalt composition and a process of making it



Ufli fid Saw Pm O 2,877,128 PAVING ASPHALT COMPOSITION AND A PROCESS OF MAKING-IT Harley F. Hardman, Lyndhurst, Ohio, assignor to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application July 5, 1955 Serial No. 520,113 3 Claims. (Cl.-'106--279).

' This invention relates to an improved petroleum asphalt paving composition and to pavements comprising .a mixture of such compositions and aggregate.

' In this country today most asphalt pavements are prepared using petroleum asphalts. Petroleum asphalt is the residuum produced by distilling off the lighter fractions of petroleum, including gasoline, kerosene, and other oils which tend to disperse the heavier, less volatile asphalt. The product frequently is blown, i. e., oxidized by blowing air through it at an elevated temperature, in order to increase its consistency to thedesired value. Many physical modifications of petroleum asphalt residuum are available and are well known to those skilled in this art. Asphalt cement, cutback asphalt, and asphalt emulsions, which are aqueous emulsions of asphalt with emulsifying agents to assist in dispersing the asphalt, are those most usually encountered. Native asphalts which have been produced by natural processes from petroleum by evaporation of the lighter components usually are" not used. They must be fluxed with lighter 'oils before they are suitable for paving purposes, and therefore present'different problems. Some so-called asphalts also are obtained from the heavier crude oil fractions by solvent extraction. These too are somewhat difierent from the ordinary residuum. Neither of these is contemplated for use in this invention. Reference to asphalt hereinafter will be'understood to refer 'to petroleum asphalt residuum only.

Over the years, through experience, a set of standards have been developed, prescribing the properties desired in petroleum asphalt for use as a paving material. These specifications do not, however, fully, define a desirable petroleum asphalt paving material. It has been noted, for example, that many paving asphalts which have a ductility below the requirements give satisfactory pavements, some of which in fact may outwear pavements made with asphalts which do meet the ductility rebut actually it does not.

quirem'ents. Many paving asphalts derived from certain crudes which meet all of the requirements are not satisfactory in cold climates, although they are fully satis factory in warm climates. Asphalts derived from California A, West Texas, and Kansas cracked crude, for example, are unsatisfactory for use in northern states such as Ohio where the pavements have to endure winter temperatures as low as 0 F. and below.

' Surfaces of bituminous pavements can'reach minimum temperatures within a few degrees of minimum air temperatures unless the temperature rapidly drops from a high -value and then rapidly rises again. the next day. Moreover, gradients as high as about 10 F; exist through a 3-inch pavement, so that the pavement must withstand not only low temperatures but temperature differentials within it. It should be noted that in considering resistance of the pavement to breaking at lowtemperatures, account must be taken notonly of resistance to stresses from the above due to the vehicles using it but also of strains caused by movement of the subsoil, particularly in early spring. These factors tend to show that flexibility of the pavement must be important. At the present time 'there is no way of measuring theability of a paving asphalt to resist such stresses.

When a pavement slab is loaded, due to astress from 2,877,128 Patented Mar. I0, 195? and deflects over a limited circular area, fas'sumingfla cupped shape in which the individual particles of ag* gregate must be spread somewhat farther apart in the horizontal direction, and somewhat closer together in the vertical direction. The particular segment of asphaltic pavement therefore must change its dimensions if it is not to break. Since the aggregate is not deformable, such movement requires movement-of the asphalt between the aggregate particles. Obviously, if the pavement is to withstand cracking under these conditions, the asphalt must retain a certain minimum degree of flexibility, and this must be retained over the entire range of temperatures to which the asphalt will be subjected. This flexibility is not fixed by current standards established for petroleum paving asphalts. v

Ductility is thought by some to measure flexibility, It measures a flow property which is somewhat difficult to define (L. Kirschbaum, Ind. Eng. Chem. 6, 976 (1914) I It is significant that those engaged in research on the problem of producing asphalts for use in cold climates have not reached an agreement on the contradictory'observations of asphalt ductility. No explanation of the contradictions has been forthcoming. It is hard to understand how a pavement having a low ductility can withstand low temperatures, and yet some do. It is suggested here that low ductility pavements which outlast high ductility pavements in cold climates and -else-' where may do so because of a higher flexibility, and that this has gone unnoticed because flexibility has not been taken into account up until now, since ductility gives no indication of flexibility.

Asphalt is composed primarily of asphaltenes and petrolenes, and is considered to be a colloidal system in which the asphaltenes constitute the dispersed phase and the petrolenes the dispersing phase. The asphaltenes are defined herein as that portion of asphalt which is soluble in carbon disulfide and insoluble in 50 volumes of n-pentane per volume of asphalt. The petrolenes are defined herein as that fraction of the asphalt which is soluble in 50 volumes of n-pentane per volume of asphalt. Asphalt can be defined in terms of other fractions, and some workers in the field have considered asphalt to be composed of asphaltenes, asphaltic resins, and oil fractions, with smaller quantities of waxes and other components. In this concept, the asphaltenes are considered as peptized by the asphaltic resins and thereby dispersed in the oil. The petrolene fraction as contemplated herein is inclusive of both the asphaltic resin and the oil fractions, together with the other components which remain in the oil phase when the asphalt is extracted with n-pentane.

Heretofore, it has been thought that the properties of the asphaltene fraction determined the suitability of the asphalt for paving, and that it was this fraction which had to be modified in order to. improve the asphalt for paving purposes. 7 g g In accordance with the instant invention, it has been determined that the flexibility of the asphalt at low tem-' peratures is determined by the properties of the petrolene fraction of the asphalt. The petrolene properties are modified, according to the invention, by incorporating in "ice ' the asphalt a primarily parafiinic hydrocarbon oil. Primarily paraffinic oils are solvents for the petrolenes, and are immiscible with the asphaltenes. The aromatic oils are solvents for the asphaltenes. These are ineffective for the purpose of increasing flexibility, i. e.,.of lower ing the flexure limit.

above or from below, it both decreases in thickness The asphalt paving composition of the invention is as flexible at low temperatures, of the order of 20 F. and below, as the unmodified petroleum asphalts are atmore elevated temperatures. The flexibility of the asphaltof the invention,..and ofsthe p vementmix. obtained by C9111:

bining such an asphalt with aggregate, may be as much as fifty times greater than astandard asphalt at the same temperature. This is a substantial diflerence, and, as might be expected, is accompanied by a high resistance to cracking at low temperatures.

This improvement in flexibility is evaluated with the aid of a special and novel test which determines the flexure limit, a characteristic determined herein for the first time, of the asphalt and of the asphalt pavement. This test is important in understanding the present invention. Without such evaluation heretofore it has been impossible to determine whether flexibility had to be improved. This test, applied to the asphalts of the invention, shows how much hydrocarbon oil to add to reduce the flexure limit of the asphalt to 20 F. or less. The results of the test have been correlated with actual experience by application of pavements of the invention which pass the test to public highways.

The test in question, referred to hereinafter as the flexure limit test, or, simply, test, is applicable both to the asphalt and to mixtures of the asphalt with aggregate. It is carried out as follows in the case of the asphalt: A sample bar of the asphalt is molded. The dimensions of the bar have been standardized at 1.25 x 1.25 x 11.5 cm. The bar is brought to the test temperature at which its flexibility is to be determined. One end is rigidly mounted in a rotatable quadrant, and the exposed end is brought sharply against the edge of an immovable object, for example, a mandrel, so placed in the path of the bar as to apply a shearing stress thereto, and so placed that if the bar can bend at an angle of 90 it will pass the object, but if it cannot bend that much it will break on contact with the object. Six samples of each asphalt are tested at a given temperature. The flexure limit is defined as the lowest temperature, in F., at which all six samples will pass the surface by bending without breaking, and the term is so used in the claims.

The test is based on the following theory. Intermediate between the solid and the gas states lie the liquid, amorphous solid and gel states. At temperatures well above the softening points, asphalts are liquid. As temperature is decreased to below the sotfening point, they gradually depart from liquid behavior, and take on more and more a type of elastic behavior characteristic of gels. At still lower temperatures they become amorphous solids, incapable of flowing under stress except at very slow rates, and exhibiting brittle fracture when overstressed. In the case of asphalt, the transition from a gel-like liquid which retains appreciable flexibility to a brittle solid occurs within a relatively short temperature range. At successively lower temperatures, as the transition progresses, the tendency of the asphalt to break increases as it is forced to bend around the fixed radius, and eventually the asphalt reaches the flexure limit, at which fracture occurs. The test thus fixes the flexure limit at the temperatures at which the flexible gel-like state passes into the brittle state. The existence of this rather sharply defined flexure limit makes it possible to define rather precisely the low temperature properties of a paving asphalt.

The flexure limits of several of the most commonly met asphalts are given in the table below:

Flexure Penetra Asphalt from Crude Limit tion at California A 50 68 Illinois Cracked 55 58 Illinois N 33 64 Kansas Cracked 52 72 Smackover 38 63 Texas 31 59 38 65 Kansas N 35 68 California B 36 87 West Texas 49 64 PanucoMexiean 31 83 These asphalts, which have known service records, show trends in the flexure limit which correspond to their performance at low temperatures. The Texas and Mexican asphalts are considered good paving asphalts in cold climates, and they have the lowest flexure limits in the group. The asphalts which are known to be worst in'cold climates have the highest flexure limits; these are the West Texas, California A and the various cracked asphalts. It will be noted that the lowest limit is 31 F. In contrast, the paving-asphalt compositions of the invention have flexure limits of 20 F., maximum, and preferably 15 F. or below.

In accordance with the invention a paving asphalt, such as any of the asphalts listed above, is blended with a primarily paraifinic liquid mineral hydrocarbon oil hav ing certain specified physical properties in an amount within the range from 10% to 40%, preferably from 15% to 30%, by weight of the asphalt blend sufficient to give the desired low flexure limit.

The hydrocarbon oil must meet the following requirements: I

(1) Pour point or solidification temperature no higher than the flexure limit required for the asphalt blend, preferably at least 5 F. less than the flexure limit, and in any event below 20 F.

(2) A flash point (Cleveland Open Cup) of at least 400 F., and preferably at least 440 F. t

(3) A viscosity no higher than 20 poises at 77 F., anjd preferably less than 5 poises at 77 F. i

(4) A viscosity index above about 40; and preferably at least 60. t

The hydrocarbon oil can be any primarily paraffinic petroleum fraction which has these properties, such as solvent extracted and conventionally refined neutral oils, bright stocks, vacuum-distilled cylinder oils, gas oils, dewaxed gas oils, wax slops fractions, and the like.

If desired, the hydrocarbon oil can be used together with an ester of an organic acid and an organic alcohol which also meets the above requirements. These are quite different from the hydrocarbon oils in their properties. However, they also are effective to lower the flexure limit.

Typical esters are the organic fatty acid esters of mono and polyhydric aliphatic and cyclic alcohols, such as glycerol monolaurate, glycerol monooleate, propylene glycol monolaurate, diethylene glycol dioleate, Cellosolve ricinoleate (ricinoleic acid ester of diethylene glycol), polyethylene glycol 200 monolaurate, polyethylene glycol di-2-ethyl hexoate, diisooctyl sebacate, tetrahydrofurfuryl oleate, butyl Cellosolve oleate (oleic acid ester of butyl ether of diethylene glycol), polyethylene glycol 400 I tallate, methyl tallate, and the naturally-occurring fats and oils having an iodine value below about 140, such as soyabean oil and cottonseed oil.

The proportions of the oil and ester are not critical, inasmuch as both are efiective for the same purpose. However, usually the oil will be in a major proportion, although mixtures containing as little as one-third oil and less are, of course, satisfactory.

It will be appreciated that the amounts of hydrocarbon oil and mixtures thereof with the ester depend upon the viscosity, softening point and other properties thereof, but the amount will be selected within the 10 to 40% range stated to produce an asphalt blend having the desired flexure limit of 20 F. or below.

After addition of the. hydrocarbon oil and/or ester, the asphalt, if necessary, will be brought to a 77 F. penetration within the paving requirements. Of course, if the mixing is done after oxidation it will be necessary to oxidize the asphalt to a lower penetration than is desired in order to meet the final penetration requirement, inasmuch as the hydrocarbon oil and/or ester will increase the penetration. For paving purposes, the asphalt blend should have a 77 F. penetration within the range from 40 to 200. r

As is well known, asphalts which are too soft can be brought to a. higher consistency by blowing with air at a temperature within the range of 375 to 500 F. This is a standard procedure and is fully set forthyin the literature. increased to the desired value. The hydrocarbon oil and the ester do not interfere with the oxidation, although there is a possibility of some loss of the hydroa carbon oil or ester during oxidation if it has a low enough boiling point. ester can be added after oxidation of the asphalt, as has been stated. 1'

The hydrocarbon oil and/or mixture thereof with the ester can be incorporated in the asphalt by any desired means. It is preferable that the asphalt be fluid, 15

and that, the blending be accompanied with sufiicient mixing to insure uniform distribution therein.v C onven: tional mixing equipment is satisfactory. If the oil andl or ester is added before the asphalt is air-blown, the airblowing .of the fluid asphalt at an elevated temperature 2 will insure adequate mixing.

The asphalt composition of the invention is intended for use in preparation of conventional asphalt aggregate paving mixes. These are well known, and a detailed description therefore is unnecessary.

from 4 to 15% asphalt and the remainder mineral aggregate or filler. The mineral aggregate and filler is selected from materials such as limestone, slag, gravel," and the like. The aggregate must meet certain specifications as to the size range of the particles, depending" upon whether the pavement is to be coarse or dense, and

Oxidation is continued until penetration has 5 To avoid this, the oil and/or v. e Asphalt pavements for road construction are prepared naphtha has been added in order to render the asphalt fluid at ordinary temperatures. After application of coldmix to a road, the solvent evaporates, leaving behind a hard asphalt surface. While cold-mix is satisfactory in certain specialized applications, it is believed by the paving industry that the most satisfactory roads are constructed with hot mix, and this invention is concerned particularly with the manufacture of hot-mix products.

Hot-mix asphalt paving mixtures are generally produced at an asphalt paving plant. Measured quantities of aggregate and asphalt cement, both at about a temperature of 300 F., are dumped into a mixer, and the mixing is usually accomplished in-a short time, on-the order. of two to five-minutes. ,The hot-mix is then dumped from the mixer into trucks or into storage bins. The trucks are usually insulated so that the mix will not lose its temperature while being transported to the actual paving site..

The following examplesare illustrative.

'Examples 1 to 16 A sample of pipestill bottoms with a 77 F. penetration in the range of 200 to 280 was oxidized by heating while blowing with air at 450 to 460 F. to a viscosity of 138 furol seconds at 300 F. This was used as a -'control.- Additional samples of the same pipestill bot- TABLE II :down to dusts of 200mesh and less.

reference. Asphalt paving mixes may be divided into twogeneral classes, i. e., hot-mix and cold-mix. The cold-mix is mineral aggregates with cut-back asphalts. I ,asphalt is a term usedv to describe conventionalasphalt compositions to which a solvent such'as petroleum tained:

Concen- Viscosity Penetration Softening Flexure Example tratlon, Hydrocarbon Oil and Ester (FSS at Point Limit No. Percent v a 300 F.) M F (P F.) I

None 13s 56 20 122 v '31 35 High V. I. thermally diffused 011.... 143. 7 270+ 215+ 141. 5 0 '30 So%1t-ex1t6gclied neutral oil, 300 133.2 119 80 127 -0 a 20 do 132.0 88 46 130 12 20 Oonventionally-reflned. neutral oil, 138.5 98 56 129 8 300 SSU at 100 F. v 30 Intermediate distillate dewaxed. 132. 0 92 58 131 7 30 Wax slope, dewaxed 135.0 84 47 126. 5 7 10 Cottonseed oil 20 Solvent-extracted neutral oil, 140 130.0 169 95 124 14 SSU at F. 9 l0 Cottonseed oi 1 20 Solvent-extracted neutral 011, 300 147.7 159 117 -6 SSU at 100 F. 1o 10 Cottonseed oil .1

"""" 20 Solvent-extracted bright stock, 78 134.6. 139 123 2 SSU at 210 0. 11 10 Cottonseed oil 20 Solvent-extracted bright stock, 250 133.0 130 111 7 .0 ha th I v o onsee o 12 g lontgtrmedigtegistmate 131.1 113 5a 120 I a o onsee o 13 23 gattngum-dilstiillled cylinder stock. 6 108 62 v o onsee o M 14 20 'Deasphalted cylinder stock I 132A 47 r 15 $8 g g gflfiff 130.0 111 51 s 16 g3 gg gg g gg 132.8 11s 56 121.6 5

may range from coarse sizes of inch in diameter in chapters II and IV of the Asphalt Handbook (1947) published by The Asphalt Institute, College Park, Maryland, the disclosuresof which are hereby incorporated by prepared at ambient temperatures by the mixing of Cutback The flexure limitof the asphalt alone (Example 1) Details are given 65 is 31 F. The asphalts oxidized in the presence of the additives of the invention are well below this, having a maximum of 14.5 (Example 14), and rangingas low as 14 F. (Example 8).

the procedures of Examples 1 to 16, using a neutral stock and a cylinder stock. The following results were ob- TABLE Cdn'cen- 77F. 77F. 140F. 3 Flexure Ex.No. t'ratlon, Hydrocarbon Oil Penetra- Duc- Stain Limit Percent tion tllity v y (i F.)

17.......{ 2o neutr alF stock, 330 SSU at] 109 100+ I s, 13

- 210 18 20 dewaxed vacuum-distilled p r cylinder stock. 92 100+ 7 14.

1 Solvent-dewax'ed at about 0 F.

The results show that both stocks are efiective. It will be noted that in these the 77 F. ductility meets the standard specifications for highway pavements.

Examples 19 to 21 In accordance with the procedure of Examples 1 to 16, a further group of asphalts was prepared using waxcontaining and dewaxed wax slops fractions, and a neu- The asphalt of the invention, Example 22, is fully com parable to Example 23 in penetration. It has a low ductility, but this is not important in view of its very low flexure limit. The difference in petrolene viscosity shows that a modification of the petrolene fraction properties is accompanied by a lowering in the fiexure limit in Example 22.

These asphalts were subjected to stability tests de-' tral stock, with the following results: signed to measure the ability of the paving mixture to TABLE IV Ooncen- Viscosity Penetra- Duc- Flexure Ex. No. tration, Hydrocarbon Oil (FSS a tion, tility, Limit Percent 300 F.) 77 F.) 77 F F.)

Wax slops 138 s3 15; 14 3O Wax slops dewaxed 135 84 37 7 20 Neutral stock, 830 122 102 100+ 13 SSU at 210 F.

All of these stocks give satisfactory results. The dewaxed wax slops fraction should be used if a high ductility product is desired.

Examples 22 to 24 of 10% cottonseed oil and 18% conventionally-refined neutral oil, 300 SSU at 100 F. starting from pipestill bottoms as the base, and compared with another sample of the same pipestill bottoms oxidized to the same penetration (Example 23) and with a standard 85/100 penetration asphalt (Example 24). All of the asphalts were air-blown to the penetration indicated in the Table withstand trafiic stresses without displacement. The measurements were made at 140 F. Values were obtained for two types of paving mixtures. Asphaltic concrete containing coarse aggregate was evaluated by the Marshall test (Proc. A. A. P. T. 17, 93 (1948)) which measures the force in pounds to break a cylindrical specimen in partially confined compression. A flow value, measuring the plasticity in 0.01 inch units, is obtained at the same time. Twenty is the maximum acceptable flow value. A sheet-asphalt mixture containing fine aggregate is used in the Hubbard-Field test which measures the pressure required to extrude the mixture through an orifice. There was no significant difference between these asphalts in these tests:

TABLE VI 'II in accordance with the procedure of Examples 1 to 16. Stability Tests, 140 F.

These asphalts had the following properties:

Exam 1e Ea 1e Exa 1 TABLE v 22 ti a? e Example Example Example Hubbard-Fieldpsd 1,100 850 1,075 No. 22 No. 23 No. 24 stability, lbs 1,240 1, 390 1,470 Marshall 7 Flow, mxmo 19 16 1s Penetration:

77-100g.5sec 12g lg hsxhef i t atsphalt. t

sp l0 0011018 e. 220 220 216 115 107 113.5 The effects of ex osure to water were determmed statill d ll I b h 0 d d ca y and ynarnica y. 11 ot cases 10 g. of stan ar 47.5 93 100 7.5 18 E reference stone (50% sillca, 50% hmestone) was coated with 5% asphalt and cooled to room temperature for 562.2 280.0 449.7 one hour, then immersed in distilled water .in sealed vjars 525:1 53 5 and kept at room temperature. For the static .test examio 74.9 45.3 nation was made for stripping at '2, '3, .and 6 weeks. For gg "55' the dynamic test the jars were rotated on a ball .mill, :SFt1air1t]llfidextg 140 F.'72 hrs.5g p. s. i 1 2 I 2 4g accelerating the strlpping by abrasive action, and examlned 8S 0111 egrees ,W v z Fire Poinflcleveland Open 605 735 715 for strlpping over a per10d of hours. In both tests the Thin Fi.lm Oxidation Penetration on 88 35 7,0 asphalt of Example 24 stripped the most severely Sand .535 3%; the asphalt of the invention, Example 22, stripped "the w r as? a ;;i,;;, 3,,.$,,, :1: 0.9414 b 5 Tddetermine if'plasticizer-migration,'i.e., exudation of Viscosity g y 'cvnstant 0-8535 0-8285 "the 1011 so that the asphalt surface becomes coverediwith awn-12s gradient from top to bottom of a pavement slab, the'asphalt was subjected to the following test. Asphalt paving mixture specimens containing each of the asphalts in question were supported on equal sized wooden plugs with thermocouples located in the surface and at the pavementwood interface. The surface was heated with infra-red lamps to 135 to 140 F., the interface temperature averag- 10 change, while maintaining good stability, and does not bleed.

Examples 25 to 27 Asphalts prepared from pipestill bottoms using inter- 5 mediate distillate and solvent extracted neutral oil are as good as wax slops. In order to showthis, asphalts were prepared from pipestill bottoms following the proing The amount of Oil 011 the Surface Was d t cedure of Examples 1 to 16 using each of these petroleum mm ed by contacting it with a stack of 30 cigarette papers fractions:

1 R & 13 Petrolene Petrolene Petrolene, Example Penetra- V1scosity Softening Ductility Flexure Percent Viscosity Viscosity 100 Vis- No. tion, (FS at Point 77 F. Limit Asphal at 100, cosity,

77 F. 300 F.) F.) F.) tenes poises poises Gravity Constant 25 Solvent extracted neutral 88 132 130 12 31 264 67 Oil, 300 SSU at 100 F. i 26 Intermediate Distillate--. 102 133 134 13 11 20 49 0.8369 27. 30% Wax Slops 83 138 128 15 13. 5 v920 120 0.8285

weighed with g. after 24 hours, and after intervals of one .and two weeks. No migration of plasticizer to the surface occurred under these conditions.

Traflic action on the pavement was simulated by placing a paving mixture on a turntable which caused the pavement to rotate while in contact with a rubber-tired wheel. Observations of the amount of additive absorbed TABLE VIII 1 R& B Petrolene Vis- Pctrolene, Example Penetra- Viscosity Softening Ductiiity, Flexure Stain Percent costty (poises) 100 Vis- No, tion, SFS at Point 77 F. Limit Index Asphalcosity,

77 F. 300 F. F.) F.) tenes Gravity 77 100 Constant 28-. 207% %elltllal stock, 330 SSU 109 118 100+ 13 6 24. 7 792 164 0. 8424 a 29 2035 vaicuifirn distilled cylin- 92 127 115 100+ 14. 5 7 23. 2 1, 072 204 0. 8344 er s cc 80 20% Neutral Stock, 330 SSU 111 118 100+ 14. 5 4 24. 2 1, 004 225 0. 8419 aotfll00 F. 10% Soyabean s1. 20% conventionally refined 69 121 127 19.5 0 21 so 224 64 0.849

' neutral oil, 300 SSU at 100 F. 10% Soyabean Oil.

by the tire were also made because rubber swells and disintegrates when it absorbs oil.

The'pavement composition used in this test was prepared as follows: The asphalt (9.5%) was mixed with 27.3% coarse sand, 47.6% fine sand and 16.6% lime: stone dust (sieve analysis: 0.5% retained on No. 8 screen, 17.5% retained on No. 40 screen, 47.7% retained on No. 80 screen, 19.8% retained on No. 200 screen, remainder 14.3% passing No. 200 screen). The mixture was heated to 300 F., mixed by hand until all of the aggregate was completely coated, reheated to 300 F. and placed in the turntable with hand compaction. The pavement was cooled to room temperature overnight, heated with an infra-red lamp to to F. and a rubber tire rotated over the pavement as the turntable revolved. The test duration was 43 /2 hours at a turntable speed of 48 R. P. M., for a total of 125,280 rotations of the wheel at approximately 20 p. s. i. There was no absorption of oil by the rubber or exudation of oil from the pavement.

Resistance to recurrent freezing and thawing was determined by the following test: Sheet-asphalt paving mixture plugs of the asphalt pavements described above were subjected to repeated cycling between -10 F. and 140 F.

The cycle took two hours. The plug containing the 140 penetration standard asphalt (Example 23) developed cracks after 15 cycles, and these continued to grow. The other two specimens (Examples 22 and 24) showed no cracks in 200 cycles. This shows the asphalt of the invention has improved resistance to temperature change.

Thus, the asphalt of the invention is improved in flexibility, water resistance and resistance to temperature The data on petrolene viscosity show that the desired low fiexure limit is obtainable at petrolene viscosities at 100 F. within the range from 64 to 225 poises.

Example 32 60 TABLE IX Viscosity (FS seconds):

350 F--- 40.0 325 F 59.7 300 F 99.4 5 250 F 368 R+B softening point, F 119.5

Penetration:

100 F.SO g.-5 sec 181 7 77 F.lOO g.-5 sec 92 32 F.200 g.60 sec 46 Ductility: 77 F.-5 ems/min 108 60 F.S ems/min 19 7 392 F.--5 ems/min 6 Fl'exure limit, F 15 Stain index, 140 F 9 Flash point, F 515 Fire point, F 600 Thin film oven test, 325 F 53 Ohio stripping test, percent coated 40-50 Percent asphaltenes 25.6

Petrolenes:

Viscosity at 77 F 331 Viscosity at 100 F 7O Specific gravity at 100 F 0.9459 Viscosity gravity constant 0.862

Oliensis Homogeneous Specific gravity, 60 F 1.004 hr. loss, percent 0.19 Percent original penetration 88.5 Thermal expansion coeflicient 5.5 Transition temperature F 38 The asphalt was used to resurface a section of existing highway. The old pavement was variable in crosssection, having been built up over the years by road mix and surface treating over gravel base. The bituminous surface ranged from 3 inches to 5%. inchesin thickness and the base ranged from 4 to 5 inches. The underlying soils are predominantly clay. The surface course was 1% inches of Ohio T-35 type C asphaltic concrete containing crushed gravel, coarse aggregate and designed for 5.8 weight percent asphalt. The material containing the above-described asphalt was laid for a distance of 2.9 miles in the north lane, alternately with paving in the south lane using an 85/100 penetration standard asphalt for comparison. The fiexure limit asphalt handled satisfactorily through the job. The only difference from the standard asphalt was that it was possible to roll the pavement somewhat sooner. The north lane pavement showed little or no sign of wear after eleven months of use, while the south lane paving developed some surface cracks.

Examples 33 to 36 A series of tests were carried out using the asphalt of Example 32 in comparison with four conventional asphalts, three (Examples 33 to 35) having penetrations within the range of 70 to 100, and the fourth (Example 36) comprising a 107 penetration asphalt base containing 10 percent of Rubarite, a synthetic rubber additive. These asphalts had the following properties:

TABLE X 10 The asphalt was tested for variation in impact strength vs. temperature. All tests were made using /1" x /2" x 6" bars prepared by casting from the molten condition. The bars were supported on rounded supports separated by 1 /2, and a 50 g. striker guided by wires 15 was allowed to fall from increasing heights until the approximate height for breaking was bracketed. The

height was then increased until six successive samples were broken at the same drop height. The data showed that the asphalt of the invention was far superior in impact resistance to all of the others studied at all temperatures from 15 F. up.

The modulus of elasticity vs. temperature was measured using an American Instrument Co. Modulimeter mounted in a constant temperature box. Bars /2" x /2" x 6" were used as test specimens. The asphalt of the in vention had a lower modulus of elasticity at all temperatures below about 25 F. than any of the other asphalts studied.

In order to demonstrate that the same results are 0b- 0 tainable when the asphalts are mixed with aggregate,

the above tests were repeated using pavement mixtures prepared as follows: 75 g. of 40-80 mesh lake sand and 15 g. of limestone dust were weighed out and each portion mixed and placed in a 325 F. oven along with a mold for a /2" x /2" x 5" bar and the asphalt to be used. When the asphalt was completely melted, 10 -g. were added to the hot sand-limestone dust blend and the ingredients mixed well with a putty knife. g. of the hot aggregate were placed in the mold and the mold sub 40 jected to 6000 p. s. i. g., hydraulic pressure in a Carver Laboratory press and allowed to come to room temperature.

In the Modulimeter test the asphalt of the invention flexed the greatest at all temperatures, and the changes in modulus elasticity from 35 F. to 0 F. were l that of the standard 108 penetration asphalt and that of the others. The asphalt of the invention showed up well under impact and constant force deformation, as well.

Example Example Example Example Example 32 33 34 35 36 80 122 88. 2 126 241 250 422 324 525 R & B Soft. Pt., F 119 110 118 Penetration:

269 2 111 80 42 18 Ductility:

775 cm./min 100+ 100+ 100+ 5 em./mi.n 100+ 100+ Flexurc Limit F. 13 22.5 32 5 Stain Index, 140. 9 5 1 Flash Point (COO), 510 600 625 Specific Gravity 77 0.987 1.002 0.996 Loss of Heating:

3255005 hrs 0. 033 0. 004 0. 013 Pen. on Residue 97 101 Percent Asphaltenea- 25. 6 22.0 v16. 8 Petrolenes, Viscosity- 154 528 2, 316 7 718 1, 960 17, 385 Petrolene, Specific Gravity at 100--. 0. 940 0. 956 0. 960

Petrolene, 100 Viscosity Gravity Constant 0.836 0.843 0.817

0. 054 0. 00s 82 so 28.3 23. 4

Examples 32 to 37 The eifect of various crude asphalt materials was determined in the following series of experiments. The crudes indicated in the table below were blended with neutral stock, 330 SSU at 100 F., 20% by weight, and the mixture oxidized at 450-460 F. with air-blowing to a viscosity of to 120430 furol seconds at 300 F. The table which follows lists the properties of the asphalts thus obtained and compares them with the properties of the crude material. Only the Santa Maria crude had a flexure limit outside the desired range. This could have been brought below 15 F. by using more of the neutral stock. In fact the fiexure limit can be adjusted as desired by varying the amount of neutral stock.

2. A process for preparing a paving asphalt composi' tion having a fiexure limit below R, which consists essentially of the step of incorporating in a petroleum residuum asphalt having a flexure limit above 20 F., a primarily parafiinic liquid mineral hydrocarbon oil characterized by a pour point below the flexure limit of the asphalt composition, a flash point (Cleveland Open Cup) of at least 400 F., a viscosity at 77 F. below 20 poises, and a viscosity index above 40, in an amount within the range from about 10% to about to reduce the iiexure limit of the asphalt to below 20 F.

3. A process in accordance with claim 2 which includes oxidizing the asphalt to a penetration at 77 F. within the range of about 40 to about 200.

TABLE XI PROPERTIES OF NORMAL PEN ASPHALT BEFORE ADDITION OF NEUTRAL STOCK I Example Example Example Example Example Example No. 32 No. 33 No. 34 No. 35 No. 36 No. 37 Talco La Columbian Santa Venezuelan Wyoming Gunlllas Maria Penetration:

77100 -5 see 86 86 92 86 102 32-200 g. w 23 21 15 1s 15 25 50 g.5 sec 131 275 R & B Softening P i 118 114 11s 1 10s l g zet ility, 77, 5 cmsJmin 110+ 110+ 110+ 110+ 100+ 100+ 350 45 2e Flexure Limit, F 33 36 41 41 41 37 Loss on Heating, 32550 gms.5 hrs-.- 0. 01 0. 04 0. 01 0. 09 0. 36 0. 01 Percent Penetration Decrease 8 9 11 12 7 13 PROPERTIES OF ASPHALT AFTER ADDITION OF NEUTRAL STOCK Penetration:

77-100 g.5 see 90 85 76 83 79 50 32-200 .-60 sec 49 49 42 40 43 35 1o0-50 .-5 w 144 137 123 150 134 37 R & B Softening Point 127 124 130 125 139 llgicttility, 77, 5 ems min 35 50 33 27 66 1s 350 48 48 45 4s 47 4s Flexure Limit, F 9 12 10 17 12 15 Stain Index, 50 p. s. 1., 72 hrs 18 17 10 8 9 14 Loss on Heating, 32550 gms.5 hrs 0. 8 0. 1 0- 8 0. 2 0. 1 0. 04 Penetration on R e 71 63 62 61 72 41 Percent Penetration Decrease 21 26 19 27 9 27 Thin Film Oven Test, 325, 5 hrs., 50 gms 05 57 55 51 52 30 Stripping Test, Percent stripped, Ohio M2051 20 10 34 0 35 15 Petrolene viscosity:

at 100 a1 42 95 49 66 41 Petrolene, 100 Viscosity, Gravity Constant 0.9312 0.9391 0. 8529 0. 8760 0. 8855 0. 8789 All proportions and percentages in the specification and References Cited in the file of this patent claims are by weight of the final asphalt composition. UNITED STATES PATENTS I claim:

1. A paving asphalt composition having a flexure limit 55 gi 3 g6 below 20 F. consisting essentially of a petroleum 1 3 061520 e a I 1919 residuum asphalt having a fiexure limit above 20 F. 1635567 ey 1927 and a primarily parafilnic liquid mineral hydrocarbon oil 1883683 g a 1932 characterized by a pour point below the fiexure limit 1982231 z 1934 of the asphalt composition, a flash point (Cleveland Open 60 2028922 C J 1936 Cup) of at least 400 F., a viscosity at 77 F. below 2392813 23; a 3 1946 20 oises and a viscosit index above 40 the said oil P Y 1 2,687,965 Sch1erme1er Aug. 31, 1954 being present in an amount within the range from about 10% to about 40% to reduce the flexure limit" of the asphalt to below 20 F.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2,877,128 March 10, 1959 Harley E, Hardman It is hereby certified that error appears in the-,printed specification of the above numbered patent requiring correction and that the said Letters Patent should read .as corrected below.

Column 2, line 18, for Kz'Lrschbaum read Kirschbraun column 3, line 43, for 'sotfening" read softening m column 11, line 35, for "through" read throughout Signed and sealed this 30th. day of June 1959,

(SEAL) Attest:

KARL LINE ROBERT c. WATSON Attesting ()flicer v Commissioner of Patents 

1. A PAVING ASPHALT COMPOSITION HAVING A "FLEXURE LIMIT" BELOW 20* F. CONSISTING ESSENTIALLY OF A PETROLEUM RESIDUUM ASPHALT HAVING A "FLEXURE LIMIT" ABOVE 20* F. AND A PRIMARILY PARAFFINIC LIQUID MINERAL HYDROCARBON OIL CHARACTERIZED BY A POUR POINT BELOW THE "FLEXURE LIMIT" OF THE ASPHALT COMPOSITION, A FLASH POINT (CLEVELAND OPEN CUP) OF AT LEAST 400* F., A VISCOSITY AT 77* F. BELOW 20 POISES, AND A VISCOSITY INDEX ABOVE 40, THE SAID OIL BEING PRESENT IN AN AMOUNT WITHIN THE RANGE FROM ABOUT 10% TO ABOUT 40% TO REDUCE THE "FLEXURE LIMIT" OF THE ASPHALT TO BELOW 20* F. 